Exploration of the cosmic microwave background has told us much about the birth of the universe. Now, the new cosmological frontier asks: How did the universe evolve after the Big Bang? When and how did the first galaxies form out of cold clumps of hydrogen gas and start to shine? That is, when did the universe’s “dark ages” end in a “cosmic dawn”? Observations and calculations suggest that this phenomenon occurred when the universe was roughly half a billion years old, when light from the first stars was able to ionize the hydrogen gas to form a sea of electrons and protons, a time known as the epoch of reionization. The HERA collaboration is building a 240-dish radio array in South Africa to explore this frontier, focusing on 21 cm radiation that will tell them the boundaries between the neutral hydrogen and the bubbles of ionized hydrogen surrounding newly formed galaxies. Once complete, in 2018, HERA will be set to answer the primary questions: What objects first lit up the universe and reionized the neutral intergalactic medium? Over what redshift range did this occur? And how did the process proceed, leading to the large-scale galaxy structure seen today? http://reionization.org/